Square wave oscillator question

[rhdwave]

Quick question about this Relaxation Oscillator circuit:



Do i need to set a Vref since it's an opamp or can i just use the positive and negative of the battery to the 7 and 4 pins

Also, if i hook an led up to the output on a breadboard, should it flash with the period or do i need to hook something up to the output first?

Much thanks for any responses!

[The Tone God]

If you hook up the positive and negative to the battery then what are you going to use for ground ? Check out the Vanishing Point v1.0 circuit on my site. I use that style of oscillator configured for battery operation.

You may be able to hook up an LED directly to the output depending on the opamp and LED you choose. If you do not require much current the most opamps should work. If you need more current then you can use a simple driver like a transistor on the output.

Andrew

[rhdwave]

Thanks Tone God!

But just from a theory perspective, in the example i posted, if it is biased to have a vref and the conditions that you stated about the opamp and type of led comply, the led should blink with the period of the oscillation, is that correct?

[The Tone God]

For that circuit to work as shown you will need a bipolar supply. If you want to run it off a single 9v battery you need to use a circuit similar to what I have posted with the 1/2 V+ bias. I believe with most opamps it will run without the added reference voltage. Adding the reference voltage will adjust the frequency of the oscillator.

Andrew